Apparatus for mounting a pellicle to a photomask and method for mounting a pellicle to a photomask

ABSTRACT

The present disclosure provides an apparatus for mounting a pellicle to a photomask, including a cover having a first side and a second side opposite to the first side, wherein the second side is configured to face the photomask, and an air pad disposed between the first side and the second side, wherein the air pad comprises a compartment filled with air.

BACKGROUND

In the semiconductor industry, there is a trend toward higher devicedensity. In order to achieve such higher density, smaller features arerequired. Such requirements frequently involve scaling down devicegeometries to achieve lower fabrication costs, higher device integrationdensity, higher speeds, and better performance. Along with theadvantages from geometry size reductions, improvements to semiconductordevices are being made.

As semiconductor industry continues to evolve, advanced photolithographytechniques have been widely used in integrated circuit fabricationoperation. Photolithography operations may include techniques pertinentto coating a photoresist layer on a wafer and exposing the wafer to anexposing source.

Masks can be used in semiconductor fabrication operations to transfer apredetermined pattern onto a substrate. For example, after forming aphotoresist layer over a substrate, the photoresist layer can be exposedto an actinic radiation through a mask, thus a photoresist pattern canbe formed by subsequent development.

In order to improve the performance of lithography operations, apellicle including a pellicle membrane can be used to alleviate theamount of particles fallen on patterns of the photomask. By keeping adistance between the particles and the pattern of the photomask, theparticles may be out of focus under exposure operations, therebyalleviating printing defects contributed by the particles.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 shows a flow chart representing method for mounting a pellicle toa photomask, in accordance with some embodiments of the presentdisclosure.

FIG. 2 is a schematic drawing illustrating an apparatus for mounting apellicle to a photomask, in accordance with some comparative embodimentsof the present disclosure.

FIG. 3 is a schematic drawing illustrating a cross sectional view of amounting plate, a pellicle and a photomask during an operation ofmounting the pellicle on the photomask, in accordance with somecomparative embodiments of the present disclosure.

FIG. 4 is a schematic drawing illustrating a cross sectional view of amounting plate, a pellicle and a photomask during an operation ofmounting the pellicle on the photomask, in accordance with somecomparative embodiments of the present disclosure.

FIG. 5A is a schematic drawing illustrating a cross sectional view of aphotomask and a pellicle after an operation of mounting the pellicle onthe photomask, in accordance with some comparative embodiments of thepresent disclosure.

FIG. 5B is a diagram illustrating deformation of the photomask inducedafter an operation of mounting the pellicle on the photomask, inaccordance with some comparative embodiments of the present disclosure.

FIG. 6A shows a flow chart representing method for mounting a pellicleto a photomask, in accordance with some embodiments of the presentdisclosure.

FIG. 6B shows a flow chart representing method for mounting a pellicleto a photomask, in accordance with some embodiments of the presentdisclosure.

FIG. 7 is a schematic drawing illustrating a cross sectional view of amounting plate, in accordance with some embodiments of the presentdisclosure.

FIG. 8 is a schematic drawing illustrating an apparatus for mounting apellicle to a photomask, in accordance with some embodiments of thepresent disclosure.

FIG. 9 is a schematic drawing illustrating an exploded view of anapparatus for mounting a pellicle to a photomask, in accordance withsome embodiments of the present disclosure.

FIG. 10A is a schematic drawing illustrating a top view of a pad, inaccordance with some embodiments of the present disclosure.

FIG. 10B is a schematic drawing illustrating a cross sectional view of apad, in accordance with some embodiments of the present disclosure.

FIG. 11 is a schematic drawing illustrating a bottom view of a cover, inaccordance with some embodiments of the present disclosure.

FIG. 12 shows a flow chart representing method for mounting a pellicleto a photomask, in accordance with some embodiments of the presentdisclosure.

FIG. 13 is a schematic drawing illustrating an apparatus for mounting apellicle to a photomask, in accordance with some embodiments of thepresent disclosure.

FIG. 14 shows a flow chart representing method for mounting a pellicleto a photomask, in accordance with some embodiments of the presentdisclosure.

FIG. 15A is a schematic drawing illustrating a lithography apparatus, inaccordance with some embodiments of the present disclosure.

FIG. 15B is a schematic drawing illustrating a lithography apparatus, inaccordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the disclosure are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in therespective testing measurements. Also, as used herein, the terms“substantially,” “approximately,” or “about” generally means within avalue or range which can be contemplated by people having ordinary skillin the art. Alternatively, the terms “substantially,” “approximately,”or “about” means within an acceptable standard error of the mean whenconsidered by one of ordinary skill in the art. People having ordinaryskill in the art can understand that the acceptable standard error mayvary according to different technologies. Other than in theoperating/working examples, or unless otherwise expressly specified, allof the numerical ranges, amounts, values and percentages such as thosefor quantities of materials, durations of times, temperatures, operatingconditions, ratios of amounts, and the likes thereof disclosed hereinshould be understood as modified in all instances by the terms“substantially,” “approximately,” or “about.” Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thepresent disclosure and attached claims are approximations that can varyas desired. At the very least, each numerical parameter should at leastbe construed in light of the number of reported significant digits andby applying ordinary rounding techniques. Ranges can be expressed hereinas from one endpoint to another endpoint or between two endpoints. Allranges disclosed herein are inclusive of the endpoints, unless specifiedotherwise.

Referring to FIG. 1, FIG. 1 shows a flow chart representing method formounting a pellicle to a photomask, in accordance with some embodimentsof the present disclosure. The method 100 for mounting a pellicle to aphotomask includes disposing a mounting plate over a first side of aphotomask (operation 101), and pressing the mounting plate against thephotomask (operation 102).

Referring to FIG. 2, FIG. 2 is a schematic drawing illustrating anapparatus for mounting a pellicle to a photomask, in accordance withsome comparative embodiments of the present disclosure. An apparatus 1 afor mounting a pellicle 12 to a photomask 10 includes a mounting plate20 a and a pellicle securing stage 32. The mounting plate 20 a includesa cover 21, wherein the cover 21 has a first side 21 a and a second side21 b opposite to the first side 21 a. The mounting plate 20 a furtherincludes a plurality of stress distributors 220 protruding from thesecond side 21 b of the cover 21 and toward the pellicle supportingstage 32. The pellicle securing stage 32 is configured to secure apellicle 12, which allows the pellicle 12 to be disposed between themounting plate 20 a and the pellicle supporting stage 32. The presser 31is configured to apply stress over the cover 21, so that the presser 31can press the mounting plate 20 a against the photomask 10 and furtherpress the photomask 10 against the pellicle 12, thereby the pellicle 12can be mounted to the photomask 10.

Referring to FIG. 3, FIG. 3 is a schematic drawing illustrating a crosssectional view of a mounting plate 20 a, a pellicle and a photomaskduring an operation of mounting the pellicle on the photomask, inaccordance with some comparative embodiments of the present disclosure.In a comparative embodiment, the mounting plate 20 a further include agel layer 23 disposed inside the cover 21 to serve as a buffer layer,wherein a top end 220 t of the plurality of stress distributors 220contacts with the gel layer 23; while a bottom end 220 b of theplurality of stress distributors 220 opposite to the top end 220 textends toward the pellicle securing stage 32 (as shown in FIG. 2). Bythe configuration of the plurality of stress distributors 220, when apresser presses the photomask 10 against the pellicle 12, the pluralityof stress distributors 220 pressed by the gel layer 23 distributes thestress toward various locations on the photomask 10. It should be notedthat in order to avoid pressing the photomask 10 against the pellicle 12with excessive pressure applied by the pellicle 12 (which may includeharder materials, such as metal), the gel layer 23 can serve as a bufferlayer with certain extent of flexibility to buffer the force appliedthereon.

Referring to FIG. 4, FIG. 4 is a schematic drawing illustrating a crosssectional view of a mounting plate 20 a, a pellicle and a photomaskduring an operation of mounting the pellicle on the photomask, inaccordance with some comparative embodiments of the present disclosure.However, after performing a plurality of mounting operations, the gellayer 23 is prone to be damaged due to stress concentration.Specifically, damages, cracks and/or cavities may be induced on (oradjacent to) a surface of the gel layer 23 contacting with some of thestress distributors 220, and the damages, cracks and/or cavities maydecrease the flexibility of the gel layer 23. Thus the gel layer 23 maynot be able to effectively buffer the force applied thereon due to lossof flexibility. In some embodiments, a bottom surface of the gel layer23 and a top surface of each of the stress distributor 220 may bemisaligned after cycles disposing the mounting plate 20 a over thephotomask 10. Furthermore, since a bottom surface of the gel layer maybe non-uniform, some of the plurality of stress distributors 220 may notbe able to distribute pressing stress since such stress distributors maynot be able to stay contact with both the gel layer 23 and the photomask10.

Referring to FIG. 5A and FIG. 5B, FIG. 5A is a schematic drawingillustrating a cross sectional view of a photomask and a pellicle afteran operation of mounting the pellicle on the photomask, and FIG. 5B is adiagram illustrating deformation of the photomask induced after anoperation of mounting the pellicle on the photomask, in accordance withsome comparative embodiments of the present disclosure. Due to thephenomena discussed in FIG. 4, the stress is not uniformly distributedin the photomask 10, and the stress may be specifically concentrated onstress distributors 220 which may have a top surface contacting thedamaged position of the gel layer 23. It can be observed that thephotomask 10 is distorted due to the non-uniform stress applied thereon,and the pattern on the photomask 10 may also be distorted, therebycausing shifting errors during performing subsequent lithographyoperations. For example, a photomask 10 may be distorted and concaveaway from the pellicle membrane 13. The comparison between a uniformphotomask 10 and a distorted photomask 10 is illustrated in the diagramof FIG. 5B. Herein a plurality of reference points is selected on theuniform photomask 10 and the arrow tails in the diagram indicates thepositions of such reference points before performing a plurality ofcycles of mounting operations. After a predetermined number of cycles ofmounting operations, the positions of the reference points are obtained,which are illustrated as the positions of arrow heads in the diagram.Alternatively stated, lengths of the arrows shown in the diagram can bedeemed as a quantification of displacement induced at each of thereference points caused by cycles of the mounting operations. In theexample provided in FIG. 5A, displacements of reference points arerelatively greater around a peripheral area than around a center area ofthe photomask 10.

In addition, users may not be able to predict when the photomask 10would be distorted to an unacceptable extent due to the damage inducedon the gel layer 23, since users may not have access to the condition togel layer 23 until the mounting plate 20 a is disassembled and the gellayer 23 is taken out and examined. Therefore, it is difficult todetermine a proper timing for the gel layer 23 replacement. It is oftentoo late to replace the mounting plate 20 a or the gel layer 23 after alarge number of devices fabricated by the distorted photomask 10 arefound defective. Furthermore, replacing the mounting plate 20 a or thegel layer 23 may cause higher cost and/or may be time-consuming.

The present disclosure provide an apparatus for mounting a pellicle to aphotomask and methods for mounting a pellicle to a photomask, whereinthe uniformity of applying stress onto the photomask is improved and therisk of inducing damage on buffer layer inside the cover of the mountingplate is reduced. Furthermore, the apparatus for mounting a pellicle toa photomask and methods for mounting a pellicle to a photomask providedin the present disclosure allows user to access the condition of thebuffer layer inside the cover of the mounting plate easily, wherein itis more convenient to inspect if there is damage to the buffer layer onregular basis (such as on daily basis, on weekly basis, or in accordancewith a predetermined schedule) without disassembling the mounting plate,and it is relatively easier to adjust the condition of the buffer layerwithout disassembling the mounting plate.

Referring to FIG. 6A, FIG. 6A shows a flow chart representing method formounting a pellicle to a photomask, in accordance with some embodimentsof the present disclosure. The method 200 for mounting a pellicle to aphotomask includes disposing a pad into the cover, wherein the padcomprises an air compartment (operation 203), supplying gas in the aircompartment (operation 206), and applying stress on the cover (operation209).

Referring to FIG. 6B, FIG. 6B shows a flow chart representing method formounting a pellicle to a photomask, in accordance with some embodimentsof the present disclosure. The method 300 for mounting a pellicle to aphotomask includes arranging a plurality of pins, wherein the pinsprotrudes from the second side of the cover through a plurality ofapertures at the second side of the cover (operation 303), disposing apad in the cover, wherein the pad is above the plurality of pins(operation 306), and applying stress on the cover (operation 309).

Referring to FIG. 7 and FIG. 8, FIG. 7 is a schematic drawingillustrating a cross sectional view of a mounting plate and FIG. 8 is aschematic drawing illustrating an apparatus for mounting a pellicle to aphotomask, in accordance with some embodiments of the presentdisclosure. An apparatus 1 b for mounting a pellicle 12 to a photomask10 includes a presser 31, a mounting plate 20 b and a pellicle securingstage 32. The mounting plate 20 b includes a cover 21, wherein the cover21 has a first side 21 a and a second side 21 b opposite to the firstside 21 a. The mounting plate 20 b further includes a plurality of pins22 protruding from the second side 21 b of the cover 21 and toward thepellicle supporting stage 32. Herein the pins may be stressdistributors. The first side 21 a of the cover 21 faces the presser 31,wherein the first side 21 a of the cover 21 contacts with the presser 31during the operation of mounting the pellicle 12 to the photomask 10.The pellicle securing stage 32 is configured to secure a pellicle 12,which allows the pellicle 12 to be disposed between the mounting plate20 b and the pellicle supporting stage 32. The apparatus 1 b may furtherinclude a photomask securer 33 between the mounting plate 20 b and thepellicle securing stage 32, wherein the photomask securer 33 secures aphotomask 10 to be disposed between the mounting plate 20 b and thepellicle 12. Alternatively stated, the photomask 10 is disposed on theother side of the cover 21 with regard to the presser 31, wherein thesecond side 21 b of the cover 21 faces the photomask 10.

The presser 31 is configured to apply stress over the first side 21 a ofthe cover 21, so that the presser 31 can press the mounting plate 20 bagainst the photomask 10 and further press the photomask 10 against thepellicle 12, thereby the pellicle 12 is mounted to the photomask 10(Which can be referred method 100 in FIG. 1). In some embodiments, thepresser 31 and the photomask securer 33 are movable, and the pelliclesecuring stage 32 may be fixed so that the pellicle 12 can be stablysupported by the pellicle securing stage 32. In some other embodiments,the presser 31, the photomask securer 33, and the pellicle securingstage 32 are movable, wherein the photomask securer 33 and the pelliclesecuring stage 32 presses against each other. The pellicle 12 includes apellicle membrane 13, wherein a distance is spacing between thephotomask 10 and the pellicle membrane 13.

The mounting plate 20 b at least includes the cover 21 and an air pad 24disposed inside the cover 21. The mounting plate 20 b may include a gasinlet 41 and a plurality of pins 22, wherein the gas inlet 41 penetratesthe first side 21 a of the cover 21, and the plurality of pins 22protruding from the second side 21 b of the cover 21 and toward thepellicle supporting stage 32. In some embodiments, the apparatus 1 b mayfurther include a pressure gauge 42 and a gas pipe 43, wherein thepressure gauge 42 can be connected to the gas inlet 41 through the gaspipe 43. The details of the gas inlet 41, the pressure gauge 42 and thegas pipe 43 will be discussed subsequently.

It should be noted that the orientation of the apparatus 1 b is notlimited. In some embodiments, the presser 31 presses the photomask 10against the pellicle 12 in a direction substantially vertical to ground,wherein the photomask 10 and the pellicle 12 are substantially parallelto ground. In some other embodiments, the presser 31 presses thephotomask 10 against the pellicle 12 in a direction substantiallyparallel to ground, wherein the photomask 10 and the pellicle 12 aresubstantially vertical to ground. In some other embodiments, the presser31 presses the photomask 10 against the pellicle 12 in any suitabledirection, and the suitable direction may be vertical to a widestsurface of the photomask 10.

Referring to FIG. 8, FIG. 9, FIG. 10A, and FIG. 10B, FIG. 9 is aschematic drawing illustrating an exploded view of an apparatus formounting a pellicle to a photomask, FIG. 10A is a schematic drawingillustrating a top view of a pad, and FIG. 10B is a schematic drawingillustrating a cross sectional view of a pad, in accordance with someembodiments of the present disclosure. In some embodiments, the cover 21includes a first portion 211 and a second portion 212, wherein an outersurface of the first portion 211 is the first side 21 a, and an outersurface of the second portion 212 is the second side 21 b. The air pad24 and the plurality of pins 22 are disposed between the first portion211 and the second portion 212. A through hole 2111 is disposed on thefirst portion 211, and the gas inlet 41 penetrates through the throughhole 2111. In some embodiments, the first portion 211 can be fixed tothe second portion 212 through an engaging axis 2119 configured toengage with the second portion 212. In some other embodiments, theengaging axis 2119 can be substituted by any other suitable fixtures orsuitable engaging mechanisms.

It should be noted that in some other embodiments, the structure of thecover 21 is not limited herein, as long as the air pad 24 can bedisposed inside the cover 21. In some embodiments, the cover 21 mayinclude three or more portions, or in some other embodiments, the cover21 can be an integrated one-piece structure. In some other embodiments,the gas inlet 41 can be placed on any other suitable position on thecover 21, such as penetrating a side surface of the cover 21, as long asthe gas inlet 21 does not substantially affect the operation ofmounting.

The air pad 24 disposed between the first side 21 a and the second side21 b includes an air compartment 240. The air pad 24 may be used as abuffer layer. In some embodiments, the air pad 24 is a hollowed tube,wherein an air pressure inside the air compartment 240 can be differentfrom the air pressure outside the air compartment 240. In someembodiments, nitrogen or condensed gas may be supplied into the aircompartment 240. In some embodiments, the air pad 24 can be made byplastic or other suitable polymer materials. In some embodiments, air(i.e. nitrogen or condensed gas) is supplied into the air pad 24subsequent to disposing the air pad 24 inside the cover 21. In someother embodiments, air (i.e. nitrogen or condensed gas) is supplied intothe air pad 24 prior to disposing the air pad 24 inside the cover 21.

The plurality of pins 22 are disposed between the air pad 24 and thephotomask 10 in order to align the relative position of the photomask 10and the air pad 24, and further distribute stress applied to thephotomask 10. The plurality of pins 22 are disposed at the second side21 b of the cover 21 and protruding from a plurality of apertures 2120configured on the second side 21 b of the cover 21. In some embodiments,the plurality of apertures 2120 may penetrate the second portion 212. Atop end 22 t of the pins 22 (shown in FIG. 7) contact with the air pad24, and a bottom end 22 b of the pins 22 (shown in FIG. 7) contact withthe photomask 10. In some embodiments, a width of the top end 22 t ofthe pins 22 is greater than a width of the bottom end 22 b of the pins22, and after disposing the pins 22 into the apertures 2120, a portionof the pins is within the cover 21 and another portion of the pins is onthe outside of the cover 21. The plurality of pins 22 may not be adheredto the surface of the apertures 2120 so that the air pad 24 can applystress over photomask 10 through the plurality of pins 22. Whenperforming a mounting operation, the presser 31 presses over the firstside 21 a of the cover 21, and the air pad 24 presses the plurality ofpins 22 against the photomask 10. The photomask 10 is pressed against tothe pellicle 12 and the pellicle 12 is thereby mounted to the photomask10.

Referring to FIG. 9, FIG. 10A and FIG. 11, FIG. 11 is a schematicdrawing illustrating a bottom view of a cover, in accordance with someembodiments of the present disclosure. An arrangement of the pluralityof pins 22 corresponds to a shape of the air pad 24, and an arrangementof the plurality of apertures 2120 corresponds to the arrangement of theplurality of pins 22. In some embodiments, since the photomask 10 isoften fabricated to have a quadrilateral shape, the air pad 24 as wellas the plurality of pins 22 is arranged in a quadrangle-shape in orderto distribute stress applied on the photomask 10 through each pin 22with improved uniformity. Accordingly, the shape of the air pad 24 maybe in a quadrangle toroid shape so that each position of the pins 22 isoverlaid with the air pad 24. In addition, each position of the pins 22is in accordance to one aperture 2120 so that the bottom ends 22 b ofthe pins 22 can be exposed from the cover 21, wherein the apertures 2120are also arranged in a quadrangle-shape manner on the second side 21 bof the cover 21. Alternatively, if the photomask is fabricated to haveother shapes different from a quadrilateral shape, the air pad and thepins are then arranged accordingly to the shape of the photomask.

In some embodiments, the air pad 24 has a constant width W from a topview perspective (as shown in FIG. 10A). Some of the plurality of pins22 may not stay in contact with the air pad 24 if width of the air pad24 varies at different positions. Stress may concentrate at thejunctions where widths vary and thus departing from the goal of applyinguniform stress from the air pad 24 to the plurality of pins 22.Therefore the uniformity of contact between the air pad 24 and theplurality of pins 22 is improved when the air pad 24 has a constantwidth W from a top view perspective, or optionally in some embodiments,when a radius (from cross sectional view) of the air pad 24 is uniform.

By aforesaid arrangement of the plurality of pins 22 and the aforesaidshape of the air pad 24, the uniformity of stress distribution appliedon the photomask 10 is improved. Specifically, since the air pad 24 isfilled by air, air substantially fills the air compartment 240uniformly. In addition, changes of pressure exerted on a local positionin the air compartment 240 may be balanced quickly and distributed tothe surroundings on inside surface of the air compartment 240.Therefore, although the presser 31 may not uniformly press the mountingplate 20 b, the air pad 24 may press the plurality of pins 22 withimproved uniformity since imbalance stress concentration may bealleviated due to the uniform pressure distribution in the aircompartment 240. Comparing to gel layer, the air pad 24 made by plasticor suitable polymer materials with adequate flexibility may provide animproved reliability under stress applied thereto, thus the risk ofinducing damage and/or cavities can be effectively alleviated.Furthermore, even if one or more pins 22 does not contact with the airpad 22 due to misalignment, uniform pressure distribution in the aircompartment 240 may alleviate the imbalance stress applied to each ofthe pins 22, thus decrease the risk of damaging the air pad 24 stemsfrom stress concentration and improve the uniformity of pressing thephotomask 10 against the pellicle 12.

Referring to FIG. 12, FIG. 12 shows a flow chart representing method formounting a pellicle to a photomask, in accordance with some embodimentsof the present disclosure. The method 400 for mounting a pellicle to aphotomask includes measuring a gas pressure of the air compartment inthe cover (operation 401), comparing the measured gas pressure of theair compartment with a predetermined value or a predetermined range(operation 403), adjusting the gas pressure of the air compartment ifthe gas pressure of the air compartment is not in the predeterminedrange (operation 406), and pressing the cover against the photomask(operation 409).

Referring back to FIG. 7 and FIG. 8, the gas inlet 41 is disposed on thefirst side 21 a of the cover 21, and the gas inlet 41 is configured toallow the pressure gauge 42 to access the air compartment 240. Forexample, a first end 41 a of the gas inlet 41 is connected to a surfaceof the air pad 24 proximal to the first side 21 a of the cover 21, and asecond end 41 b of the gas inlet 41 can be connected to the pressuregauge 42 through the gas pipe 43. By accessing the air compartment 240through the gas inlet 41, the pressure gauge 42 can measure a gaspressure in the air compartment 240. The gas pressure of the aircompartment 240 can be deemed as an indication of whether the air pad 24is damaged, leaked, deflated, or improperly inflated. In someembodiments, in order to improve the uniformity of contact between thepins 22 and the air pad 24, the gas pressure of the air compartment 240is measured prior to pressing the cover 21 against the photomask 10, sothat the gas pressure of the air compartment 240 can be adjusted to bein a predetermined range. A target gas pressure of the air compartment240 is lower than a predetermined upper threshold value, and greaterthan a predetermined lower threshold value. Herein the predeterminedupper threshold value and the predetermined lower threshold value arerelated to the shape, the size, and/or the material of the air pad 24.If the gas pressure of the air compartment 240 is greater than thepredetermined upper threshold value, the pressure of air pad 24 appliedon the plurality of pins 22 may be too great, or the air pad 24 may beunder the risk of bursting or being damaged due to overpressure. If thegas pressure of the air compartment 240 is less than the predeterminedlower threshold value, the deflation of air pad 24 may affect thecontact engaging with the plurality of pins 22 or may not be able toproperly distribute stress over the plurality of pins 22 against thephotomask 10. In some embodiments, the gas pressure of the aircompartment 240 being less than the predetermined lower threshold valuemay also be an indication of gas has been/is currently leaking out dueto damage (such as crack or hole induced on the air pad 24). It shouldbe noted that by filling the air pad 24 with air, even leakage isinduced, the apparatus 1 b, the photomask 10 or workpieces (i.e.substrate or wafer) in the apparatus 1 b may not be contaminated by thefiller inside the air pad 24.

In some embodiments, the measurement of the gas pressure of the aircompartment 240 can be performed prior to pressing the cover 21 againstthe photomask 10. In some embodiments, the measurement of the gaspressure of the air compartment 240 can be performed on a predeterminedschedule. In some embodiments, the measurement can be performed by apredetermined frequency, such as on daily basis or on weekly basis. Insome embodiments, the measurement prior to mounting the pellicle 12 tothe photomask 10. In some embodiments, the measurement subsequent to apredetermined cycles of mounting the pellicle 12 to the photomask 10. Insome other embodiments, the measurement can be performed during theoperation of mounting the pellicle 12 to the photomask 10. In some otherembodiments, the measurement can be constantly performed to inspect thegas pressure of the air compartment 240 instantly.

Referring to FIG. 13, FIG. 13 is a schematic drawing illustrating anapparatus for mounting a pellicle to a photomask, in accordance withsome embodiments of the present disclosure. As previously discussed inFIG. 12, the gas pressure of the air compartment 240 is adjusted to bein the predetermined range subsequent to measuring the gas pressure ofthe air compartment 240. If a measured gas pressure of the aircompartment 240 is greater than the predetermined upper threshold value,the gas pressure of the air compartment 240 is adjusted to be less thanthe predetermined upper threshold value. If a measured gas pressure ofthe air compartment 240 is less than the predetermined lower thresholdvalue, the gas pressure of the air compartment 240 is adjusted to begreater than the predetermined lower threshold value. For exemplarydemonstration, the predetermined upper threshold value is set to beabout 2.0 Bar, and the predetermined lower threshold value is set to beat least 0.0 Bar. However, the predetermined upper threshold value andthe predetermined lower threshold value may be adjusted based on one ormore properties of the air pad 24.

In order to adjust the gas pressure of the air compartment 240conveniently (for example, not required to disassemble the cover 21 insome embodiments), the second end 41 b of the gas inlet 41 is connectedto a gas presser adjuster 49 through a gas pipe 43′, wherein the gaspresser adjuster 49 may include an gas supply source (which may providegas, such as nitrogen or condensed gas). In some embodiments, the gaspresser adjuster 49 may provide pressure relief configured to exhaustair in the air compartment 240. In some other embodiments, the air inthe air compartment 240 can be released into ambient environment throughthe gas inlet 41 or the gas pipe 43′.

Subsequent to adjusting the gas pressure of the air compartment 240, thepresser 31 presses the mounting plate 20 b, and the mounting plate 20further presses the photomask 10 against the pellicle 12. Thereby thepellicle 12 is mounted on the photomask 10.

Referring to FIG. 14, FIG. 14 shows a flow chart representing method formounting a pellicle to a photomask, in accordance with some embodimentsof the present disclosure. The method 500 for mounting a pellicle to aphotomask includes pressing a mounting plate against a photomask tomount a pellicle on the photomask (operation 501), forming a photoresist layer over a substrate (operation 503), exposing the photo resistlayer with actinic radiation by using an optical lithography tool(operation 506), and developing the exposed photo resist layer to form aresist pattern (operation 509).

Referring to FIG. 15A and FIG. 15B, FIG. 15A is a schematic drawingillustrating a lithography apparatus, FIG. 15B is a schematic drawingillustrating a lithography apparatus, in accordance with someembodiments of the present disclosure. The pellicle 12 is mounted to thephotomask 10 by methods previously discussed in FIG. 6A to FIG. 13. Theactinic radiation source 1110 is configured to radiate an actinicradiation 1111, wherein the actinic radiation 1111 may include extremeultraviolet (EUV), krypton fluoride (KrF) laser, argon fluoride (ArF)laser, deep ultraviolet (DUV), or other suitable light utilized inphotolithography fabrication. In some embodiments, a mask stage 51inside a photolithography processing chamber 2 may be configured toaccommodate the photomask 10 (as discussed in FIG. 6A to FIG. 13) underan actinic radiation source 1110. The actinic radiation 1111 passesthrough the photomask 10 and the pellicle 12 mounted on the photomask 10(as shown in FIG. 15A). In some other embodiments, the actinic radiation1111 passes through the pellicle and reflected by the photomask 10,wherein the photomask may be secured by a chuck 51′ (as shown in FIG.15B). A substrate 91 with a photoresist layer 92 formed above thesubstrate 91 is accommodated under the photomask 10 by a substratesupporter 52, so that the photoresist layer 92 can be irradiated by theactinic radiation 1111 through the photomask 10 (as shown in FIG. 15A)or reflected from the photomask 10 (as shown in FIG. 15B) in order toform a predetermined pattern. In some embodiments, one or more opticaldevices, such as lenses, reflection mirrors, beam splitters, beamexpanders, polarizers, or wave plates, can be disposed on a path of theactinic radiation 1111 from the actinic radiation source 1110 to thephotoresist layer 92 to alter a property of the actinic radiation 1111.For example, one or more lens can be used to adjust the focus of theactinic radiation source 1110.

The present disclosure provide an apparatus 1 b for mounting a pellicle12 to a photomask 10 and methods for mounting a pellicle 12 to aphotomask 10, wherein the uniformity of applying stress onto thephotomask 10 is improved and the risk of inducing damage on the air pad24 inside the cover 21 of the mounting plate is reduced. In addition, bythe configuration of the plurality of pins 22 and the air pad 24 asdiscussed in FIG. 7 to FIG. 11, the uniformity of stress distributionunder pressing operation can be improved.

Furthermore, the apparatus for mounting a pellicle to a photomask andmethods for mounting a pellicle to a photomask provided in the presentdisclosure allows the access to obtain the gas pressure of the aircompartment 240 of the air pad 24 inside the cover 21 withoutdisassembling the mounting plate, and it is relatively easier to adjustthe gas pressure of the air compartment 240 of the air pad 24 withoutdisassembling the mounting plate. When the gas pressure of the aircompartment 240 is out of a predetermined range, the gas pressure of theair compartment 240 is adjusted before fabricating photomask 10, thuscan alleviate the risk of producing massive amount of defectivesemiconductor devices with distorted photomask due to the unknown andundesired condition of the mounting plate used in the fabrication of thephotomask 10.

Some embodiments of the present disclosure provide an apparatus formounting a pellicle to a photomask, including a cover having a firstside and a second side opposite to the first side, wherein the secondside is configured to face the photomask, and an air pad disposedbetween the first side and the second side, wherein the air padcomprises a compartment filled with air.

Some embodiments of the present disclosure provide an apparatus formounting a pellicle to a photomask, including a cover having a firstside and a second side opposite to the first side, wherein the secondside is configured to face photomask, and a gas inlet on the first sideof the cover.

Some embodiments of the present disclosure provide a method for mountinga pellicle to a photomask, including disposing a pad into a cover havinga first side and a second side opposite to the first side, wherein thepad comprises an air compartment, supplying gas into the aircompartment, and applying stress on the cover.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother operations and structures for carrying out the same purposesand/or achieving the same advantages of the embodiments introducedherein. Those skilled in the art should also realize that suchequivalent constructions do not depart from the spirit and scope of thepresent disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

What is claimed is:
 1. An apparatus for mounting a pellicle to aphotomask, comprising: a cover having a first side and a second sideopposite to the first side, wherein the second side is configured toface the photomask; and an air pad made of a flexible material disposedbetween the first side and the second side, wherein the air padcomprises a compartment filled with air.
 2. The apparatus of claim 1,further comprising a plurality of pins disposed between the air pad andthe photomask.
 3. The apparatus of claim 2, wherein the plurality ofpins protrude from the second side through a plurality of apertures atthe second side of the cover.
 4. The apparatus of claim 3, wherein anarrangement of the plurality of apertures corresponds to a shape of theair pad.
 5. The apparatus of claim 2, wherein the plurality of pins arearranged in a quadrangle-shape.
 6. The apparatus of claim 1, furthercomprising a gas inlet penetrating the first side of the cover.
 7. Theapparatus of claim 1, further comprising a presser over the first sideof the cover, wherein the presser is configured to apply stress over thefirst side of the cover.
 8. An apparatus for mounting a pellicle to aphotomask, comprising: a cover having a first side and a second sideopposite to the first side, wherein the second side is configured toface the photomask, and a plurality of apertures are configured topenetrate the second side of the cover; a gas inlet on the first side ofthe cover; and a plurality of pins, each of the pins is placed in theaperture and has a top width at a top end, the top width is greater thana width of the aperture.
 9. The apparatus of claim 8, further comprisingan air pad disposed between the first side and the second side of thecover, wherein the air pad comprises an air compartment.
 10. Theapparatus of claim 9, wherein the air compartment of the air pad isfilled with at least one of the nitrogen gas and condensed gas.
 11. Theapparatus of claim 9, wherein the air pad has a constant width from atop view perspective.
 12. The apparatus of claim 9, wherein the gasinlet is configured to allow a pressure gauge to access the aircompartment.
 13. The apparatus of claim 9, wherein each of the pluralityof pins has a bottom width at a bottom end opposite to the top end, thebottom width is less than a width of the aperture.
 14. A method formounting a pellicle to a photomask, comprising: disposing a flexiblematerial in a cover, wherein the cover has a first side and a secondside opposite to the first side; supplying gas into an air compartmentsurrounded by the flexible material; and applying stress on the cover.15. The method of claim 14, further comprising pressing the coveragainst the photomask.
 16. The method of claim 15, wherein pressing thecover against the photomask comprises pressing a plurality of pinsprotruding from the second side of the cover against the photomask. 17.The method of claim 15, further comprising measuring a gas pressure ofthe air compartment prior to pressing the cover against the photomask.18. The method of claim 17, further comprising increasing the gaspressure of the air compartment when a measured gas pressure of the aircompartment is lower than a predetermined value.
 19. The method of claim17, further comprising decreasing the gas pressure of the aircompartment when a measured gas pressure of the air compartment isgreater than a predetermined value.
 20. The method of claim 14, furthercomprising aligning the flexible material with the photomask bydisposing a plurality of pins at the second side of the cover.